PIEZOELECTRIC VIBRATOR AND MANUFACTURING METHOD THEREOF

A crystal vibrator (1, 51) includes an upper and a lower substrate (3, 4, 53, 54) overlaid on the upper and the lower surface of an intermediate crystal plate (2, 52) formed by a crystal vibration piece (5, 55) and an external frame (6, 56) which are formed as a unitary block. These components are bonded hermetically. The upper and the lower substrate respectively have an indentation opposing to the intermediate crystal plate. The recesses define cavities (16, 66) for hermetically sealing the crystal vibration piece in a floating state. The upper and the lower bonding surface of the intermediate crystal plate are subjected to mirror finishing, after which a conductive film (9, 11) is formed. Each of the bonding surfaces of the upper and the lower substrate is a crystal surface subjected mirror finishing. In another embodiment, metal thin films (67 to 69) are formed on each bonding surface of the upper and the lower substrate subjected to the mirror finishing. The upper and lower substrate and the intermediate crystal plate have bonding surfaces subjected to surface activation by plasma treatment. Then the three of them are simultaneously subjected to pressure or each of the three is successively subjected to pressure at room temperature (or while being heated) so as to be bonded hermetically. The cavity is sealed as a vacuum or an inert gas atmosphere.